Textbook of Engineering Drawing, Second Edition

__ Lettering and Dimensioning Practices 2.7

Precedence of Lines

1. When a Visible Line coincide with a Hidden Line or Center Line, draw the Visible Line.
   Also, extend the Center Line beyond the outlines of the view.


2. When a Hidden Line coincides with a Center Line, draw the Hidden Line.


3. When a Visible Line coincides with a Cutting Plane, draw the Visible Line.


4. When a Center line coincides with a Cutting Plane, draw the Center Line and show the
   Cutting Plane line outside the outlines of the view at the ends of the Center Line by thick
   dashes.

2.3 LETTERING [IS 9609 (PART 0) : 2001 AND SP 46 : 2003]

Lettering is defined as writing of titles, sub-titles, dimensions, etc., on a drawing.

2.3.1 Importance of Lettering

To undertake production work of an engineering components as per the drawing, the size and

other details are indicated on the drawing. This is done in the fonn of notes and dimensions.

Main Features of Lettering are legibility, unifonnity and rapidity of execution. Use of drawing
instruments for lettering consumes more time. Lettering should be done freehand with speed.
Practice accompanied by continuous efforts would improve the lettering skill and style. Poor lettering
mars the appearance of an otherwise good drawing.

BIS and ISO Conventions

IS 9609 (Part 0) : 2001 and SP 46 : 2003 (Lettering for technical drawings) specifY lettering in

technical product documentation. This BIS standard is based on ISO 3098-0: 1997.

2.3.2 Single Stroke Letters

The word single-stroke should not be taken to mean that the lettering should be made in one stroke

without lifting the pencil. It means that the thickness of the letter should be unifonn as if it is

obtained in one stroke of the pencil.

2.3.3 Types of Single Stroke Letters

1. Lettering Type A: (i) Vertical and (ii) Sloped (~t 750 to the horizontal)


2. Lettering Type B : (i) Vertical and (ii) Sloped (at 750 to the horizontal)
   Type B Preferred
   In Type A, height of the capital letter is divided into 14 equal parts, while in Type B, height of the
   capital letter is divided into 10 equal parts. Type B is preferred for easy and fast execution, because
   of the division of height into 10 equal parts.
   Vertical Letters Preferred

Vertical letters are preferred for easy and fast execution, instead of sloped letters.